Division A Commission 19 WG Theory of Earth Rotation
Universidad de Alicante
Depto de Matematica Aplicada
Escuela Politécnica Superior
Campus de San Vicente. PO Box 99
Phone: +34 96 590 3731
Fax: +34 96 590 9707
Organization website: http://web.ua.es/wgther
September 19, 2013
Jet Propulsion Laboratory
Geodynamics and Space Geodesy Group
Mail Stop 238-600
4800 Oak Grove Drive
Phone: +1 818 354 4010
Fax: +1 818 393 4965
Organization website: http://www.jpl.nasa.gov/index.cfm
April 16, 2013
Terms of Reference:
1. A main objective of the Working Group (WG) is to assess and ensure the level of consistency of ERP predictions derived from theories with the corresponding ERPs determined from analyses of the observational data provided by the various geodetic techniques. Consistency must be understood in its broader meaning, referring to models, processing standards, conventions etc.
2. Clearer definitions of polar motion and nutation are needed for both their separation in observational data analysis and for use in theoretical modeling.
3. Theoretical approaches must be consistent with IAU and IAG Resolutions concerning reference systems, frames and time scales.
4. Searching for potential sources of systematic differences between theory and observations is encouraged, including potential effects of differences in reference frame realization.
5. The derivation of comprehensive theories accounting for all relevant astronomical and geophysical effects and able to predict all ERPs is sought. In case more than one theory is needed to accomplish this, their consistency should be ensured.
6. There are no a priori preferred approaches or methods of solution, although solutions must be suitable for operational use and the simplicity of their adaptation to future improvements or changes in background models should be considered.
7. The incorporation into current models of corrections stemming from newly studied effects or improvements of existing models may be recommended by the WG when they lead to significant accuracy enhancements.
1. Contribute to improving the accuracy of precession-nutation and ERP theoretical models by proposing both new models and additional corrections to existing models.
2. Clarify the issue of consistency among conventional ERPs, their definitions in various theoretical approaches, and their practical determination.
3. Establish guidelines or requirements for future theoretical developments with improved accuracy.
It is clear that the overall goals of the Working Group cannot be achieved within only 2 years, but the first term (until the next General Assembly of both IAU and IAG, i.e., mid 2015) of the WG should be used to develop a solid concept of how to reach its aims.
Structure and operation:
Chair: Jose M. Ferrándiz (IAU)
Vice-Chair: Richard Gross (IAG)
We are awarwe that the proposed subject is too broad for a single WG, and also that the existence of independent WGs for different sub-fields implies a risk that their results will not be consistent with each other. Thus, we propose to establish one WG with the following three Sub-WGs:
1. Precession/Nutation (Chair: Juan Getino)
2. Polar Motion and UT1 (Chair: Aleksander Brzezinski)
3. Numerical Solutions and Validation (Chair: Robert Heinkelmann)
SWG 3 will be dedicated to numerical theories and solutions, relativity and new concepts and validation by comparisons among theories and observational series. The subjects of SWG 1 and 2 are self explanatory.
These SWGs should work in parallel for the sake of efficiency. To guarantee that the SWGs are linked together as closely as the needs of consistency demand, the Chair and Vice-chair of the WG, Ferrandiz and Gross, will be involved in all SWGs as will the President of C19, Chengli Huang. And a number of people will be members of more than one SWG.
Division A Commission 19 Rotation of the Earth